Chelsea and Barcelona's recent rivalry reignited at Stamford Bridge on Wednesday night, but it began in 2005 as Jose Mourinho and Frank Rijkaard clashed over accusations that the Barca manager had spoken to referee Anders Frisk at half-time. The two games - culminating in a wonderful 5-4 win for the Blues on aggregate - were quickly overshadowed by events off the pitch that turned the clubs into two of the most bitter rivals in European football.

Before the turn of the millennium, Chelsea and Barcelona had only ever faced each other in one competition, the 1966 Fairs Cup semi-final, when a Joaquim Rife-inspired Barcelona side won out 5-0 in a replay after the first two meetings had finished 2-0. Barca went on to win the competition and, coming as it did in the Real Madrid dominated mid-1960s, it was a rare trophy for the Blaugrana. Little did anyone know that the rivalry between Barcelona and Chelsea would brew less than half a century later.

Before Roman Abramovich had ever considered making a move to London to make Chelsea his plaything, the club were fighting for glory among the best in Europe for the first time as their debut Champions League campaign arrived after a third-place finish in the 1998-99 season.

Under the management of Gianluca Vialli, Chelsea's run to the quarter-finals that season was full of memorable moments - a famous Dennis Wise equaliser away at Milan's San Siro stadium, Galatasaray's noisy support silenced by a 5-0 win in Turkey - but the crowning achievement was a 3-1 win over tournament favourites Barcelona in the quarter-final first leg at Stamford Bridge thanks to a Gianfranco Zola goal and a brace from Tore Andre Flo.

The Guardian's Martin Thorpe wrote: "On one of the finest nights in the club's history, Chelsea proved beyond doubt that they can live with the very best in Europe. They scored three goals in eight minutes just before half-time to consign Barcelona to their first defeat in this season's competition."

But all hopes of reaching the semis would come crashing down at the Camp Nou as the Catalans put on a masterclass to leave the Londoners ''outclassed and largely outfought''. A 3-1 scoreline after normal time meant an additional half hour and Rivaldo's penalty, along with a Patrick Kluivert header, sent Barca through. The referee that day: a certain Anders Frisk, for whom the tie would take on added meaning in the years to come.

Indeed, by the next time the two teams clashed in 2005, much had changed. Barcelona had failed to win anything after parting company with Louis van Gaal in the summer of 2000 (though he returned for a short spell) but a new era was dawning after the appointment of Frank Rijkaard in 2003. Chelsea, meanwhile, had been busy building an empire, and the arrival of Abramovich's billions had brought about a dramatic transformation.

Under Jose Mourinho, the Blues were on the verge of claiming a record points tally of 95 in winning the Premier League - their first title in half a century. A star-studded Barcelona, meanwhile, were also closing in on their first La Liga crown since 1999. All signs pointed to a titanic clash, which was ultimately overshadowed by controversy. Boldly, Mourinho got the fireworks underway as he named Barcelona's side at the pre-match press conference, while Rijkaard insisted: "Usually when people talk, it is a sign that they are not very calm."

Ultimately, the first leg, a 2-1 win for Barca, was a tight affair heavily influenced by the sending off of Didier Drogba for a second yellow card after 56 minutes. The Guardian's Kevin McCarra wrote: "Jose Mourinho had never before lost two matches in a row as a manager, but he may yet bless the narrowness of this defeat which leaves his team well placed for the return leg. He should save all his curses for Didier Drogba."

Bless he did not. Instead, Mourinho cursed the officials for Drogba's cards and in particular referee Anders Frisk, whom he accused of allowing Rijkaard into his dressing room at half-time. The Portuguese manager refused to speak to the media after the game, but wrote in his column for newspaper Dez Record in his homeland a few days later: "When I saw Rijkaard entering the referee's dressing room I couldn't believe it. When Didier Drogba was sent off (after half-time) I wasn't surprised."

Chelsea stood by their man and chief executive Peter Kenyon revealed that the club would report their concerns to UEFA. "We as a club are putting in a report," he told BBC Five Live's Sportsweek. "There was an incident at half-time which we weren't happy with. It was a real situation and we're making a point, not an official complaint."

Labelling Mourinho's behaviour ''pathetic'', Barcelona assistant coach Henk ten Cate hit back, while Rijkaard himself played down any role in the incident. "There was a lot of talking before the game and now surprisingly there is a lot of talking after the game. It is not good behaviour after a match," he said. "Maybe they want to start something and make it worse than it is. I really don't understand it. I am calm about it."

Ahead of the return leg on March 8, though, the war of words had reached fever pitch. Mourinho, undaunted, continued his criticism of Frisk by dismissing suggestions that he had called for the world's top official, Pierluigi Collina, to referee the return leg. Instead, he responded dryly: "I would like Frisk as the ref. Perhaps he would help us like the way he helped [Barcelona] in Spain."

The repeated condemnation was not received well by UEFA, with the director of communications William Gaillard suggesting on the day of the game: "I don't think it is very helpful to keep on criticising the work of a referee like Frisk. To suggest he influenced the game in Barcelona is an unacceptable comment."

Mourinho was later handed a two-match ban for his comments, but was pitchside for the game at Stamford Bridge, and Collina was indeed in charge, although he could do little to halt the carnage that followed.

A blistering start saw Chelsea take a 3-0 lead inside the first 20 minutes. Goals from Eidur Gudjohnsen, Frank Lampard and Damien Duff ensured that the Blues were doing their talking on the pitch, although they were pegged back to 3-2 before half-time through the magic of Ronaldinho. The Brazilian coolly converted a questionable penalty awarded against Paulo Ferreira for a handball, before an innovative static toe-poke levelled the tie at 4-4 on aggregate. Barca, though, were still ahead on away goals.

Then, in the 76th minute, the blue touch paper was lit: John Terry leaped highest to head home from a corner to make it 4-2 and put the Blues ahead again, but Barcelona's players were incandescent as they believed Chelsea centre-back Ricardo Carvalho had obstructed goalkeeper Victor Valdes by holding him back. Collina remained unmoved.

Oddly in a game of such twists and turns, there were no more goals. However, as the final whistle blew and Mourinho ran onto the pitch to celebrate, it all kicked off on the touchline. Rijkaard and Chelsea scout Andre Villas-Boas confronted each other, while Barca striker Samuel Eto'o was the centre of attention after he was accused of spitting at stewards and in turn claimed to have been racially abused.

The Cameroon striker was furious after the game and, although there was no evidence to substantiate his claims of racism, revealed: "Mourinho is shameless. If this team wins the Champions League, it would make you want to retire. With so much money and so many players, what they do is not football."

Reflecting on the game - and the war of words beforehand - Rijkaard added: "You always feel bitter after a loss, but maybe I feel a bit more bitter because of all the lies that were told before this game. I suppose all the stuff surrounding the game wants you to win a bit more, and makes it hurt more when you lose. These things happen when people show their emotions sometimes."

What happened next? Despite the fact that the game was over, and Chelsea were through, the recriminations continued. Frisk retired on March 12 because of death threats from fans and said: "I've been subjected to things that I couldn't even imagine. I love to referee and I have done it since 1978, but what has happened to me over the last 16 days means it is not worth continuing. I won't ever go out on a football pitch again. I am too scared. It is not worth it. Unfortunately that is the way football looks in 2005. I've had enough. I don't even dare let my kids go to the post office."

Claim and counter claim followed, with UEFA official Volker Roth calling Mourinho "an enemy of football" (a claim not endorsed by his organisation), and the Portuguse was eventually charged for his comments on April 1. With controversy following them everywhere that season, Chelsea eventually fell to Liverpool in the semi-finals, courtesy of Luis Garcia's famous 'ghost-goal'.

Their war with Barcelona reconvened as the Catalans got revenge the following season as Mourinho accused Lionel Messi of getting Asier Del Horno sent off and, in 2009, Tom Henning Ovrebo was the subject of the Blues' ire as he was branded a disgrace by Didier Drogba after failing to give decisions their way before Andres Iniesta's last-gasp goal knocked them out in another high-profile semi.